Survey data can be collected and processed to produce a representation (e.g. image) of a subterranean structure. In some implementations, survey data includes seismic survey data collected using seismic survey equipment. The seismic survey equipment includes one or more seismic sources that are activated to produce seismic waves propagated into the subterranean structure. A part of the seismic waves is reflected from the subterranean structure and detected by seismic sensors that are part of the survey equipment.
Seismic surveying can be performed in a marine environment. An issue associated with marine seismic surveying is the presence of ghost signals. Ghost signals refer to signals in measurement data resulting from reflections from an air-water interface of the marine environment. A seismic wave generated by a seismic source is propagated generally downwardly into the subterranean structure. A reflected seismic wave (that is in response to the seismic wave propagated by the seismic source) propagates generally upwardly toward an arrangement of seismic sensors. In the marine environment, the seismic wave reflected from the subterranean structure continues to propagate towards the air-water interface, where the seismic wave is reflected back downwardly.
This reflected, generally downwardly traveling seismic wave is detected by the seismic sensors as ghost signals appearing in measurement data collected by the seismic sensors. The presence of ghost signals can result in reduced accuracy when generating a representation of the subterranean structure based on the measurement data.